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In a monochromatic liquid crystal display (LCD), such as those used in calculators, the purpose of the liquid crystal is to A. change colour from white to black when a segment is to be displayed. B. lubricate the small gap between the plates to prevent overheating. C. rotate the plane of polarization of the light passing through it. D. act as a conducting pathway between the segment electrodes.

A stationary loudspeaker emits sound of frequency of 1000 Hz. Nadine attaches the loudspeaker to a string. She moves the loudspeaker in a horizontal circle above her head at a speed of 30 m s–1. The speed of sound in air is 330 m s–1. An observer is standing well away from Nadine. Determine the maximum frequency of the sound heard by the observer.

1100 Hz

James is wearing polarized sunglasses and views the sunlight reflected from

the smooth surface of a lake.

The angle θ is the angle between the surface of the lake and James’s

line of sight. Calculate the value of θ at which the reflected sunlight

from the surface is minimized. The refractive index of the water is 1.3.

38°